When a mental health professional asses a defendants competency, they should use one of several specialized instruments designed specifically for the purpose of evaluating how well a defendant understands the charges and potential proceedings. these specific test and interviews have made competency more reliable, valid, and useful. Competency evaluations are sometimes complicated by such factors as malingering, amnesia, and the problem of whether incompetent defendants can be treated again their will. Other competency issues (eg. competency to refuse insanity defense and competency to be sentenced) can side at different points in the criminal process.